NMR rapid detection of Salmonella in milk based on ultra-small iron oxide nanobiosensor

The monitoring and control of foodborne pathogenic microorganisms to protect food safety is of great significance. A biosensor based on superparamagnetic ultra-small iron oxide nanoparticles (USIO NPs) combined with membrane filtration and low field nuclear magnetic resonance (LF-NMR) for rapid detection of Salmonella is introduced. First, free biotin-capture-antibodies and biotin-detection-antibodies were specifically bound to different targets of Salmonella in milk samples. Then streptavidin-coated USIO NP probes were coupled with the biotinylated monoclonal antibody to capture Salmonella . Finally, polyethersulfone membrane filtration was performed on the final reaction system to remove unbound-probes, and the transverse magnetisation time (T 2 ) of the filtrate was measured by NMR to indirectly reflect the content of the target substance retained on the filter membrane. This method shows high specificity and anti-interference to Salmonella , and the limit of detection (LOD) in pure culture and real samples was 2.3 × 10 3   cfu  mL −1 within 150 min.